1. Field of the Invention
The present invention relates to electrophotographic recording of images and, more particularly, to an image receiving sheet and recording process for use in elecrophotographic recording of images.
2. Description of the Related Art
Practical processes for forming full color electrophotographic images using three colors of yellow, magenta and cyan (or four colors including black in addition to the above three colors) have been recently developed. The image receiving sheet used in electrophotography usually comprises a receptor layer formed on a substrate to securely record and hold letters, pictures, and other information. The image receiving sheet is applied to an overhead projector as an information transmission means for use in meetings, schools, companies, and other presentations and exhibitions.
When a full color electrophotographic image is projected with an overhead projector, the projected image shows a gray tone (i.e., graying), thereby resulting in a narrow color-tone reproduction range. The graying results from toner particles attaching to a smooth image receiving surface of the image receiving sheet and not being sufficiently embedded in the receptor layer of the image receiving sheet to be smoothed by the heat when fixing the toner. Instead, the toner particles protrude from the surface of the sheet, thereby making the surface uneven and scattering incident light during image projection. Consequently, shadows are formed on the screen.
In an exemplary technique for solving the above graying problem, Japanese Laid Open Patent Publication No. 02-263642, which is related to Japanese Patent Publication No. 2,633,023 and U.S. Pat. No. 5,032,440 (all three of which are hereby incorporated by reference) discloses the use of a resin binder having a storage elasticity modulus ranging from 100 to 10000 dye/cm2 at 160xc2x0 C. while having larger storage elasticity modulus than that of the toner resin at a fixing temperature of the toner. The fixing temperatures in current electrophotographic techniques, however, widely vary within a range from 140xc2x0 C. to 195xc2x0 C. depending on types of apparatus. Therefore, a clear projected image cannot be always obtained merely by a prescribed storage elasticity modulus at 160xc2x0 C.
While many technologies for softening the receptor resin for solving the graying problem have been proposed, no technology has succeeded in preventing the graying problem. In one technique, the toner is smoothed by increasing the fixing temperature and pressure, thereby reducing light scattering. However, since the receptor layer is transferred to the fixing roller in the resin binder used in the conventional image receiving sheet, the receptor layer readily offset the fixing roller. While an oil is used during the fixing process for preventing offset of the resin for improving parting property of the roller, an excess amount of the oil not only allows image quality to deteriorate but also interferes transfer of the image receiving sheet.
The smoothing procedure as described above is useful for fixing the toner without using any oils.
Accordingly, the present invention is directed to an image receiving sheet and recording process that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an image receiving sheet and a recording process that prevents offset of the receptor layer to the fixing roller, has good color repeatability, and produces clear images without graying.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an image receiving sheet comprises a substrate having at least one face; and a receptor layer having a binder resin, the receptor layer provided on the face of the substrate, wherein the binder resin of the receptor layer has storage elasticity moduli of 104 Pa or more at 130xc2x0 C. and 102 Pa or more at 200xc2x0 C.
In another aspect, a recording process for forming an image comprises the steps of providing an image receiving sheet, the image receiving sheet including a substrate having at least one face and a receptor layer provided on the face of the substrate such that the receptor layer has a binder resin with storage elasticity moduli of 104 Pa or more at 130xc2x0 C. and 102 Pa or more at 200xc2x0 C.; transferring toner particles onto the receptor layer to form a pattern of the toner particles corresponding to the image to be recorded on the image receiving sheet; and embedding the toner particles into the reception layer at a fixing temperature between 130xc2x0 C. and 200xc2x0 C. to fix the toner particles to the image receiving sheet.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.